1. Field of the Invention
The present invention relates to light amount control of illumination light in a fundus camera, and more specifically, to a light metering area used to control an amount of illumination light.
2. Description of the Related Art
Conventional fundus cameras are configured to set a predetermined amount of light to use according to when the camera changes a photographing method, such as a color photographing mode and a visible fluorescent photographing mode, or performs microcoria photographing, or changes a magnification ratio of photographing.
In the field of fundus camera, technology to control an amount of light for photographing by detecting return light from a fundus is also known.
As an example of the control technology, Japanese Patent Publication No. 03-032367 discusses a fundus camera which receives light reflected from a fundus at a plurality of points located in an area having a diameter larger than that of an optic disk and determines an amount of exposure so as not to be affected by the optic disk portion.
Japanese Patent Application Laid-Open No. 09-131321 discusses an ophthalmological examination apparatus that changes a reference value of an amount of light to be received during fluorescence imaging according to insertion and removal of an excitation filter and a barrier filter to/from an optical path.
In these fundus cameras, if a subject's eye has a pupil of a small diameter, a light blocking member is switched to one of a smaller size so that illumination light can reach the fundus of the eye. In this case, however, the illumination light reflected at the cornea and the crystalline lens of the eye may appear as a flare at the peripheral part of a fundus image to be obtained. In addition, the switching of the light blocking members may cause changes in brightness distribution of the fundus image.
A brightness distribution of a fundus image varies depending on the ways of focus adjustment, one way with a focus target projected onto a fundus, and another way without use of the focus target. Thus, insertion and removal of a focus target may affect light metering values to be used.